B(C6F5)3: a robust catalyst for the activation of CO2 and dimethylamine borane for the N-formylation reactions

Abstract

In this work, B(C₆F₅)₃ is utilized as an organocatalyst for the transition-metal-free N-formylation of amines using carbon dioxide (CO₂) as a C1 source and dimethylamine borane (Me₂NH·BH₃) as a green hydrogen transfer source at 80 °C. Most reported works utilize silane and hydrogen for the N-formylation reactions using CO₂ which have thus far been limited by low atom economy, high cost or the use of harsh reaction conditions. This catalytic protocol affords a broad range of formylated products in moderate to excellent yields under mild reaction conditions with a high TON and TOF. The bulky boron (B(C₆F₅)₃) catalyst reacts with amines and forms a Frustrated Lewis Pair (FLP) and activates CO₂ and Me₂NH·BH₃ molecules. Additionally, this boron catalyst shows high catalytic activity for the cyclization of o-phenylenediamines using CO₂ and Me₂NH·BH₃ to synthesize benzimidazoles.